1. Field of the Invention
The present invention relates to a lateral displacement preventing device for a stabilizer, which prevents a stabilizer that is used as a shock absorber for a wheel in a vehicle or the like from changing position in an axial direction at the time of travel.
2. Description of the Related Art
FIG. 2 is a perspective view of a stabilizer 1 shown in Japanese Patent Application Laid-Open (JP-A) No. 2000-79819. The stabilizer 1 is a type of torsion spring made of a bar, the whole of which is elastic, and formed in a squared U-shape by bending both end portions 3,3 in the same direction at right angles with respect to a central base portion 2. The central base portion 2 is pivotably supported at a vehicle body structure and both end portions 3,3 are connected to an axle.
The stabilizer 1 is configured so as to convert energy generated by the rolling motion of the vehicle body at the time of travel into torsional motion of the base 2 and absorb the same. However, when lateral displacement occurs in which the stabilizer 1 changes position in the axial direction of the base portion 2, the axle is affected, and traveling performance is deteriorated. Therefore, there is need to prevent lateral displacement in which the stabilizer 1 is displaced in the axial direction of the base portion 2. As one means for preventing this lateral displacement, a means has been used wherein flange-shaped portions 4 having an increased diameter are locally formed in the vicinity of a position at which the base portion is pivotably supported, and side surfaces of these flange-shaped portions 4 are made to abut against a member at the vehicle body floor structure side.
Further, as another lateral displacement preventing device, a device shown in JP-A No. 2000-142068 is known. That is, as shown in FIG. 3, a means has been used wherein an inner ring member 5 made of rubber or the like having a large coefficient of friction is wound at the vicinity of the position at which the base portion of the stabilizer 1 is pivotably supported, a central portion outer periphery of the inner ring member 5 is tightly wrapped with a sheet metal band 6, and frictional resistance force is added to a fixing surface 7 so as to prevent the inner ring member 5 from sliding with respect to the base member 2, and a side surface of the inner ring member 5 is made to abut against a pivoted member at the vehicle body floor structure side.
Furthermore, as another lateral displacement preventing device, a device shown in U.S. Pat. No. 5,857,800 is known. Conventionally, as shown in FIG. 4, a flat plate 8 is plastically deformed into a C-shape and clamped around the slider 1, and both end faces of the flat plate 8 are welded to each other with a weld metal W. However, since the surface of the stabilizer 1 is directly exposed at a gap of a seam of the both end faces of the flat plate 8, there is a risk of the weld metal directly contacting the surface of the stabilizer 1 from that gap at the time of welding. In a case where the weld metal has directly contacted the surface of the stabilizer 1, the most conspicuous effect is change in the surface hardness of the stabilizer 1, and, as a result thereof, there is potential for becoming an origin of breakage of the stabilizer 1. Moreover, since the lateral displacement preventing device is installed in the vicinity of a position at which the torsion generated stress of the stabilizer 1 is highest, this becomes a cause of marked reduction in the durability life span of the stabilizer 1.
This will be explained using one example of experimental results. When divided according to the weld metal, the heat affected zone (HAZ region, i.e., the region of change in hardness due to thermal effect), and the stabilizer base material, the change in surface hardness at the weld portion is as shown in FIG. 5. That is, the surface hardness exhibits the highest hardness in the HAZ portion, and this portion is likely to become an origin of breakage. Note that, in FIG. 5, the range of 0.0 to 1.6 mm in depth from the surface on the horizontal axis is the original stabilizer base material, and 0.0 to −1.6 mm represents the raised portion of weld metal.
In U.S. Pat. No. 5,857,800, it is disclosed that, in order to avoid adverse effects at the time of welding, two halved rings 9,10 are connected at a hinge portion 11, the hinge portion 11 is plastically deformed, and welding is carried out at a weld portion 12 provided at an opposite side from the hinge portion, as shown in FIGS. 6A and 6B.
In the lateral displacement preventing device shown in FIG. 2, since compression direction thrusting force is applied to the base portion 2 of the stabilizer 1 to plastically deform the same, there is a problem in that a production process is complicated. In the lateral displacement preventing device shown in FIG. 3, large clamping force cannot be expected of the sheet metal band 6, and thus, there is a problem in that the inner ring member 5 slides when it receives a large lateral direction force. In the lateral displacement preventing device shown in FIG. 4, as discussed above, heat at the time of welding is directly transmitted to the stabilizer 1 and has adverse effects on the stabilizer 1. In the lateral displacement preventing device shown in FIGS. 6A and 6B, the half-ring form is complicated, and thus the device becomes costly. Further, a certain amount of space is necessary for providing the weld portion 12, and this is disadvantageous from the standpoint of securing space.